Studies are proposed to identify and characterize cellular mechanisms through which polypeptide hormones and cyclic nucleotides regulate cell growth and differentiated function. Functional bovine and human fetal and definitive zone adrenocortical cell cultures are used in these studies. The effects of oxygen and free radicals on cytochrome P-450 enzymes involved in steroid production are being studied. Factors regulating fetal zone growth and function are being investigated. Studies of cAMP- and CGMP-dependent protein kinases focus on structure/function analysis and regulatory factors.